The lining of the mouth and pharynx of vertebrates contains clusters of chemoreceptive cells, called taste buds. Taste buds differentiate directly from the epithelium that lines the oro-pharyngeal cavity. In amphibians, the oro-pharyngeal epithelium develops from the anterior endoderm of the embryo. Cultures of the anterior endoderm produce taste buds without influence from other embryonic tissues. Because these cultures produce a mixture of both taste buds and epithelium, this implies that decisions are made within this tissue which result in some cells becoming taste buds while others become epithelial cells. I propose to examine the role of cell-cell interactions in the specification of taste bud precursor cells (Aim 1). Preliminary experiments have shown that disruption of normal cell contacts during a critical stage of development causes an increase in the number of taste buds produced by the anterior endoderm. The increase in taste bud number observed upon disruption of cell contacts is reminiscent of the effects seen upon disruption of Notch/Delta mediated lateral inhibition. I will determine whether genes involved in the Notch signaling pathway are present in the anterior endoderm during the critical period for cell contacts (Aim 2). Finally, if members of the Notch signaling pathway are present in the anterior endoderm during the critical period I plan to investigate what role they may play in specifying taste bud precursor cells (Aim 3).